There are more commercial applications for electron linacs than for any other type of particle accelerator. To date, over 1000 linacs have been installed in hospitals throughout the United States. Although these hospitals use linacs primarily for medical therapy, the devices also find applications in industrial settings and in the scientific community. Electron linacs are useful in the areas of atomic research, electron beam therapy, X-ray therapy, diagnostics, sterilization, polymerization, synchrotron light sources, free electron lasers, and accelerating structures for microtrons.
Linac art may be categorized by wave properties, yielding standing wave linacs and traveling wave linacs. Alternatively, accelerators may be classified according to particle velocities. In general, low-beta accelerators operate at less than half the speed of light, whereas high-beta linacs operate at higher speeds.
Most contemporary standing wave, high-beta linacs utilize a side-coupled cavity configuration which was invented at Los Alamos Meson Physics Facility in the mid-60's. Although exemplary, this structure is not ideally suited for certain specific applications. For instance, side-coupled linacs are heavy, fragile, and expensive. The cavity configuration is inherently difficult to fabricate, requiring relatively complex, expensive, and labor-intensive manufacturing techniques. Furthermore, the structure is heavy, fragile, and very difficult to tune.
For further information concerning the operation and structure of prior art linacs, reference may be made to "High Energy Accelerating Structures for High Gradient Proton Linac Applications" by Manca et al., IEEE Transactions on Nuclear Science, Vol. NS-24, No. 3, June 1977, pp. 1087-1090 and "PIGMI: A Pion Generator for Medical Irradiations" by Swenson, Los Alamos National Laboratory, Pub. LAL-81-6, Feb. 1981.